Experimental investigation of bio-based PCM for energy-efficient building envelopes

This study experimentally evaluates the thermal and mechanical performance of cement mortar enhanced with a bio-based shape-stabilized composite phase change material (SSCPCM) for passive cooling in building envelopes. A eutectic mixture of lauric acid and beeswax (LA–BW) was developed, exhibiting a melting temperature of 38.7 °C and latent heat of 242.3 J/g. The eutectic PCM was impregnated into zeolite, and the optimal composite, containing 35 wt.% PCM loading was selected based on leakage resistance at 70–75 °C. This SSCPCM exhibited a melting temperature of 36.3 °C, a latent heat of 84.6 J/g, and maintained stability after 750 thermal cycles. The SSCPCM was incorporated into cement mortar at varying replacement levels, and mortars containing moderate SSCPCM content retained a 28-day compressive strength of 79–95 kN, which is sufficient for interior plaster applications. To assess real-world performance, the optimized SSCPCM-mortar was applied as an 8-mm-thick interior plaster layer in test chambers exposed to natural climatic conditions in Varanasi, India. The PCM-integrated mortar achieved a peak indoor temperature reduction of 6.3°C and a peak temperature delay of 78 min compared to the reference mortar, demonstrating significant attenuation of heat gain under hot-humid conditions.